This study proposes a prospective longitudinal follow-up of 275 children and adolescents and their parents, all of whom were studied with an extensive battery of structured clinical interviews and self-report questionnaires 3-6 years ago. All subjects received criterion-based lifetime and current diagnoses and were assessed in multiple domains of functioning. Full 3- generation pedigrees (N= more than 2,000) were constructed by history for each family. These families form several important comparison groups, including a clinically-based sample of families with one or both parents who have had an affective illness (probands, relatives and controls from the Boston Center of the NIMH-CRB Program on the Psychobiology of Depression), and two random samples (one from the community and one from a prepaid health maintenance organization). Thus, the sample for the proposed research includes a wide range of combinations of parental affective illness, non-affective illness and families in which neither parent has had any diagnosable psychiatric illness. The initial assessment study is completed and the data have been fully analyzed. The preliminary studies and significance sections describe the results in detail and explicate how they support the proposed application. The aims of this proposal are to: 1. study psychopathology in children by observing prospectively the course and outcome of preexisting disorders and the onset of new disorders; 2. identify the clinical and familial predictors of first onset, course and outcome of childhood affective illness; 3. test the nosologic validity of distinguishing between dysthmia and major depression and of the primary/secondary subtype of major depression; 4. determine the power of parental and sibling illness in predicting the onset and course of psychopathology and adaptive functioning in children; and 5. discover the stability of the child's and parent's report of psychopathology after five years. This proposal consists of two phases; 1. a "blind" initial reassessment of all children and adolescents and an all sources of information follow-up on their parents, and 2. subsequent semi- annual followup evaluations of all children/adolescents and their parents. In concentrating on manifest psychopathology and psychosocial functioning, we will be using semi-structured diagnostic and psychosocial interviews. Child and parents will be followed in parallel fashion and concurrent timelines will be used to record levels of psychopathology, psychosocial functioning and treatment for each family member.